1. Field of the Invention
The present invention relates generally to a wireless power transmission and reception technique applied to a wireless charging technique, and more particularly, to an over-voltage protection device for a transmission device in a resonant wireless power transmission and reception technique and a method for controlling the over-voltage protection device.
2. Description of the Related Art
A wireless charging (or non-contact charging) technique using wireless power transmission and reception has recently been developed and used for various electronic devices. The wireless charging technique allows a user to automatically charge a battery by simply placing it on a charging deck without connecting a device such as a cellular phone, to a separate charging connector.
Wireless electric toothbrushes and wireless electric shavers are commonly known devices that use the wireless charging technique. The wireless power transmission and reception technique may increase sealing force and waterproof features as it wirelessly charges electronic products and thus does not need an external charging terminal, and may also increase portability of electronic devices because it does not require wired chargers. The wireless charging related technique is expected to evolve significantly in the growing era of electric vehicles.
The wireless charging technique roughly includes an electromagnetic induction scheme using coils, a resonant scheme using resonance, and a Radio Frequency (RF)/microwave radiation scheme that converts electrical energy into a microwave and transfers the energy. An electromagnetic induction-based power transmission method involves transferring power between a primary coil and a secondary coil. The resonant scheme uses frequency resonance between a transmission device and a reception device that use a resonance frequency.
In the wireless power transmission and reception technique, when abnormal conditions occur, such as incorrect placement of a reception device on a charging deck of a transmission device, the reception device is abnormal, or a metallic substance is placed on the charging deck, excessive power beyond a normal value may be generated in the reception device. Therefore, a wireless power transmission and reception system as well as the reception device essentially require an over-voltage protection circuit.
For the over-voltage protection circuit, a Zener diode may be included in the reception device. However, the Zener diode needs a preparation period corresponding to a time necessary for its operation, and in that preparation period, over-voltage protection is difficult to achieve. Moreover, as the amount of power to be handled increases, the size and capacity of the required Zener diode also increases. In this case, there may be significant restrictions on a mounting size.
Such restrictions make it difficult to include a corresponding wireless power reception device in a portion of an electronic device for which a size limitation is vital. As such, there is a need in the art for an over-voltage protection circuit capable of achieving rapid handling and having high efficiency while reducing a mounting size in wireless power transmission and reception devices.